The hair cuticle provides significant protection from external sources, as well as giving rise to many of its bulk properties, e.g., friction, shine, etc. that are important in many industries. In this work, atomic force microscopy-infrared spectroscopy (AFM-IR) has been used to investigate the nanometer-scale topography and chemical structure of human hair cuticles in two spectral regions. AFM-IR combines atomic force microscopy with a tunable infrared laser and circumvents the diffraction limit that has impaired traditional infrared spectroscopy, facilitating surface-selective spectroscopy at ultra-spatial resolution. This high resolution was exploited to probe the protein secondary structures and lipid content, as well as specific amino acid residues, e.g., cystine, within individual cuticle cells. Characterization across the top of individual cells showed large inhomogeneity in protein and lipid contributions that suggested significant changes to physical properties on approaching the hair edge. Additionally, the exposed layered sub-structure of individual cuticle cells allowed their chemical compositions to be assessed. The variation of protein, lipid, and cystine composition in the observed layers, as well as the measured dimensions of each, correspond closely to that of the epicuticle, A-layer, exocuticle, and endocuticle layers of the cuticle cell sub-structure, confirming previous findings, and demonstrate the potential of AFM-IR for nanoscale chemical characterization within biological substrates.

中文翻译：

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EXPRESS：使用集成原子力显微镜和红外激光光谱 (AFM-IR) 对头发角质层细胞进行纳米级分子表征

毛鳞片提供了对外部来源的显着保护，并产生了其在许多行业中很重要的许多整体特性，例如摩擦、光泽等。在这项工作中，原子力显微镜 - 红外光谱 (AFM-IR) 已被用于研究两个光谱区域中人类头发角质层的纳米级形貌和化学结构。AFM-IR 将原子力显微镜与可调谐红外激光相结合，绕过了传统红外光谱受损的衍射极限，促进了超空间分辨率的表面选择性光谱。这种高分辨率被用来探测单个角质层细胞内的蛋白质二级结构和脂质含量，以及特定的氨基酸残基，例如胱氨酸。单个细胞顶部的表征显示蛋白质和脂质贡献存在很大的不均匀性，这表明在接近头发边缘时物理特性发生了显着变化。此外，单个角质层细胞暴露的分层子结构允许评估它们的化学成分。观察到的层中蛋白质、脂质和胱氨酸成分的变化，以及每个层的测量尺寸，与角质层细胞亚结构的上表皮、A 层、外表皮和内表皮层的变化密切对应，证实先前的发现，并证明了 AFM-IR 在生物基质内纳米级化学表征方面的潜力。